The present invention relates to a technique of enhancing the adhesion between a substrate (such as a semiconductor substrate, a glass substrate for a liquid crystal display device, a glass substrate for a photomask) and a coating film formed on a surface of the substrate.
Products such as semiconductors and liquid crystal displays are manufactured by performing a series of process steps including cleaning, resist coating, exposure, development, etching, formation of interlayer dielectric films, thermal process, dicing and the like on substrates.
Rapid progress in the integration of semiconductor devices and the like in recent years requires finer patterns of resist masks. In response, as for a light source of an exposure device responsible for exposure process, a deep UV light source such as a KrF excimer laser light source or an ArF excimer laser light source for emitting light with a relatively short wavelength is becoming a mainstream light source in place of a conventionally employed ultraviolet lamp. However, even an ArF excimer laser light source cannot satisfactorily respond to the current need for still finer patterns. This may be satisfied by employing a light source with a shorter wavelength such as an F2 laser light source in the exposure device. Meanwhile, immersion exposure process has been suggested as an exposure technique that realizes much finer patterns while allowing reduction in cost burden.
In the immersion exposure process, a gap between a projection optical system and a substrate is filled with a liquid greater in refractive index n than air (n=1) such for example as pure water with a refractive index n=1.44, and then “immersion exposure” is performed. This increases a numerical aperture to realize resolution enhancement. According to this immersion exposure process, even with the use of a conventionally employed ArF excimer laser light source (with a wavelength of 193 nm), the equivalent wavelength is shortened to 134 nm. This realizes finer patterns of resist masks while suppressing the increase in cost burden.
When the immersion exposure process is employed, a liquid directly contacts a surface of a substrate at the time of exposure. In order to protect a resist film, a resist coating film is formed on a substrate surface in some cases. The resist coating film is arranged on the top layer of the resist film, and is removed at the time of development. A technique related to the formation and removal of a resist coating film is disclosed for example in Japanese Patent Application Laid-Open Nos. 2007-96155 and 2007-96156.
The adhesion between a resist coating film and a substrate is not generally strong. Thus, a resist coating film is quite likely to peel off from a substrate surface, which has been conventionally seen as a problem. If a formed resist coating film peels off prior to exposure, the protection of a resist film cannot be achieved.